(1) Field of the Invention
The present invention relates generally to package sorting conveyors and, more particularly, to a system for adjusting and monitoring the distance between adjacent carts.
(2) Description of the Related Art
Conveyor systems having a number of individual carrying carts have been commonly used for many years to carry and sort packages or other items, such as mail. For example, U.S. Pat. No. 5,054,601 to Sjogren et al. discloses a package sorting conveyor comprised of a train of tilt tray carriers coupled in tandem to form a continuous loop. Each carrier includes a pivotally mounted tilt tray normally maintained in an upright position. The carriers are moved around the loop by a series of motors spaced around the loop. Branching out from the loop are outfeed chutes or the like for receiving packages from the carriers. When a particular carrier holding a particular package to be sorted reaches a selected outfeed chute, an actuator tilts the tray to dump the package into the outfeed chute. Another example of a typical package sorting conveyor is disclosed in International PCT Application Number PCT/DK90/00047 of Kosan Crisplant A/S, now U.S. Pat. No. 5,664,660.
Tilt tray sorters are installed as a closed-loop system. The track upon which the tilt trays are carried is manufactured to a fixed predetermined length based on the customer's specific requirements and building layout. Tilt trays are built upon a carrier or chassis assembly that is also of fixed length (typically twenty or twenty-four inches). Therefore, a particular track length is designed to have a certain number of tilt tray carriers. For example, if a particular application requires a trick length of 525 feet, and the application requires a tilt tray on a twenty-four inch chassis, the track will be engineered to be either 524 feet or 526 feet, and will hold either 262 or 263 tilt tray sorters, respectively.
A difficulty has arisen in the installation of tilt tray sorter conveyors, and installing them on the prospective site. Typically, because of site variables and manufacturing tolerances, the installation of the carriers upon the track does not match in the field. During installation, it is not uncommon for the track to be short or long by several inches.
The solution in the past was to build a “TAKE-UP” using two expansion joints, which would allow the track installers to move large sections of track, after installation, to correct for the variables. The take-up was a movable platform, typically under a curved section of track. The track was fitted with expansion joints as necessary at each end of the curve. If the track needed to be lengthened, the curve was physically picked up and moved to extend the track, and expansion joints were placed on the track where it was lengthened. If the track needed to be shortened, portions of the track could be machined and the curve physically picked up and moved to shorten the track. The location of the expansion joint or machining caused a problem because of the noise that would be generated as the carts would move over this section of track. All of this was time consuming and required skilled experienced labor.
Rather than lengthening or shortening the track, a second way to accommodate for this installation variable was to lengthen the train of carts. This was done by installing spacers in the linkage of the carriers. The typical carrier has a form of ball joint connection between the carriers. In certain systems, the trailing carrier had a ball assembly, on an extending rod bolted to the axis frame. Adding spacers between the extending rod and the frame could effectively lengthen the extending rod. For example, if the track were two inches longer than anticipated, the installation team would install thirty-two {fraction (1/16)}th inch spacers on carts throughout the train. Arranging the spacers uniformly throughout the train of carriers was found to be preferable. The installation team would remove the extending rod on the chosen carriers, add a spacer, and reinstall the extending rod.
Several problems have been noted with this procedure. First, access was difficult to the location of the connection between the extending rod and axis frame. The installers were forced to partially disassemble the tilt tray carrier in order to remove the extending rod. Second, once the spacers were installed, there was no visual indicator as to which carts were modified with the spacers. If a carrier were to need replacement, or if the bolt failed, there was no indicator that the particular cart had been effectively lengthened with a spacer.
Thus, there remains a need for a new and improved sorting conveyor in which the spacing between adjacent carts may be easily adjusted while, at the same time, the gap between adjacent carts may be monitored.